The present invention relates to an aperture for a projection exposure apparatus which is used to form fine patterns on a semiconductor wafer and to a method for forming a fine pattern on a semiconductor wafer.
In the field of an exposure processes, various technological improvements have been proposed from the view point of achieving a good resolution and a optimum depth of focus (DOF).
To obtain a good resolution and optimum DOF, various aperture configurations are disclosed in Japanese Laid Open Patent Publication: HEI5-275315, published on Oct. 22, 1993, and HEI7-29788, published on Jan. 31, 1995.
The aperture configuration is important in obtaining good resolution and the DOF characteristics. This is because an angle of light which is applied to a mask carrying a circuit pattern depends on the configuration of the aperture.
The first object of the invention is to provide an aperture which is used in an exposure process of a semiconductor manufacturing process, and which makes it possible to achieve a good resolution and an optimum depth of focus.
The second object of the invention is to provide a method for forming a fine pattern on a semiconductor wafer with using an improved aperture.
To achieve the first object, in a typical embodiment of the present invention, an aperture is comprised of a light transmissive region which is defined by first, second, third and fourth curves.
To achieve the second object, in an exposure process of a semiconductor manufacturing process, the exposure is carried using an aperture that has a light transmissive region which is defined by first, second, third and fourth curves, being interposed between a light source and a semiconductor wafer.
According to this invention, during the exposure process, each curve of the light transmissive regions contributes to an improvement in the resolution and optimum depth of focus (DOF).